The invention relates to a method and an apparatus for the regulation of turbochargers and internal combustion engines associated with such turbochargers, all of which are presented hereinafter and finally claimed. It is known to dispose the turbine part of an exhaust turbocharger in the exhaust tube of an internal combustion engine, the charging or compression area of which is oriented toward the intake manifold of the internal combustion engine in such a manner that the engine can be supplied with the required combustion air at an increased charge pressure, so that there is a general increase in output of the engine as a result of such charging.
In such an arrangement, the charging of the engine is dependent on the turbocharger rpm at a particular time, which results in the following problems. It is possible that the turbocharger may be endangered because it may be supplied with excess energy as a result of high exhaust gas temperatures, and thus exceed its limit rpm. The engine as well, which may preferably be embodied as a Diesel engine, is endangered if as a result of the turbocharger there is such a high air charging that the permissible compression and combustion pressure in the cylinders is exceeded. There are difficulties in general, over the entire rpm range of the engine, in attaining a favorable adjustment of the behavior of the exhaust turbocharger, particularly in an Otto engine, where in order to attain sufficiently high torque at low rpm a relatively small exhaust turbocharger must be used. In that event, the exhaust turbocharger supplies too much air at high engine rpm, so that the torque of the engine at high rpm is too high and it is also to be understood that the rpm of the exhaust turbocharger and the exhaust gas temperature can become impermissibly high.
The same is basically true in providing a Diesel engine with an exhaust turbocharger, which should supply sufficient air for sufficient torque even at low engine rpm, however with such a device an undesirably large air quantity at high rpm is produced. Although it is possible in a Diesel engine to determine the torque behavior of the engine by limiting the fuel quantity, still the rpm of the exhaust turbocharger can become impermissibly high. In addition, the high combustion pressure in the combustion chamber of the engine requires a stable engine structure. It is desirable in general to limit the air throughput in such a way that in a Diesel engine the fuel burns with little smoke.
There is a known means of control of the exhaust gas delivery to an exhaust turbocharger by subdividing the exhaust tube ahead of the turbocharger turbine and forming a so-called bypass line, which, as may be desired, diverts a portion of the exhaust quantity from passing through the turbine of the exhaust turbocharger. To this end, in a known manner, a bypass valve controlled by the charge pressure of the compressor part of the exhaust turbocharger can be disposed at the branching point of the bypass line. This bypass valve opens either fully or partially under very high charge pressure and diverts certain exhaust gas quantities away from the turbine of the exhaust turbocharger, thus bypassing it. In so doing, however, there is the disadvantage that such a means of regulation does not rely on actual conditions, and in particular those of the rpm of the engine or the induced air quantity or the rpm of the turbocharger; in addition, external air pressure variations enter into the regulation and act as an interference factor.